The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a transponder key ecu that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the ecu sends a signal to the ecm to prohibit fuel delivery and ignition, effectively disabling the engine.

The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then the signal is transmitted to the ecu. The ecu matches the key's id code with the vehicle's id code, which was previously registered in the ecu and then communicates the results to the ecm using sfi communication.
Engine immobiliser system
How to proceed with troubleshootingSkid control sensor (for 2wd)
Components
Removal
Hint:
Use the same procedures for the lh side and rh side.
The procedures listed below are for the lh side.
Disconnect cable from negative battery
terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery termin ...
Knock sensor 1 circuit
Description
Flat type knock sensors (non-resonant type) have structures that can detect
vibrations over a wide band
of frequencies: between approximately 6 khz and 15 khz.
A knock sensor is fitted onto the engine block to detect engine knocking.
The knock sensor contains a piezoelectri ...
Front fog light circuit
Description
The main body ecu controls the front fog light relay (marking: fr fog) when a
signal is received from
the headlight dimmer switch.
Wiring diagram
Inspection procedure
Perform active test by intelligent tester
Connect the intelligent tester (with can vim) to the
dlc3 ...